The present invention relates to a cold cathode discharge tube, and more particularly to a cold cathode discharge tube capable of operating at a frequency higher than conventional.
A conventional cold cathode discharge tube has a structure as shown in FIG. 2. The cold cathode tube 20 has electrodes 20a whose terminals 20b extend to the outside of a glass envelope 20c. The cold cathode tube 20 starts operating when a high frequency power outputted from an inverter 21 is applied across the terminals 20b via leads 22. Distributed capacitance of the leads 22 cannot be neglected because a high frequency output power is used. Therefore, a ballast capacitor 21a has heretofore been added to the inverter 21 for compensating for the distributed capacitance of the leads 22.
If the output frequency of the inverter 21 is high, the inverter and its peripheral system can be made small in size. Thus, it is preferable to use as high a frequency as possible. However, with the above conventional cold cathode discharge tube, the higher the frequency becomes, the greater becomes the influence of the distributed capacitance of the leads 22, so that the ballast capacitor 21a becomes unable to compensate for the phase delay, thus resulting in insufficient starting voltage and failure of operating of the tube. As above, the conventional cold cathode discharge tube has a limit of allowable frequency, and of miniaturization of the inverter and its peripheral system.